In general, light-emitting diodes (LEDs) have relatively low brightnesses and relatively short lives at relatively high temperatures. In the case of LED retrofit lamps, a heat sink is used to dissipate heat or cool the LED(s). However, the space available for the heat sink is limited by a usually standardized outer contour of the lamp to be replaced and by the amount of space required for a bulb and driver electronics. Owing to the physical limitation, the size of the volume of the heat sink which can be used effectively for cooling is limited, and thus so is the cooling power. In the case of LED lamps with a standard-limited size, the power of the light source and therefore the brightness are limited corresponding to the limited cooling power.
US 2007/0080362 A1 has disclosed an LED arrangement with a high-power LED chip, which has a first surface and a second surface, the second surface being fitted to a substrate. The second surface is in close thermal contact with an optically transmissive heat sink, which has a thermal conductivity of more than 30 W/(m·K). Providing the optically transmissive heat sink can double the thermal conduction of the LED die, which increases the life, efficiency or luminous intensity or an equilibrium comprising these three factors.